I'd agree with @jbrennand that it is over-utilisation. As the pattern is worst during working hours, but less pronounced during the evening (when content streaming is the predominant use of capacity) I suspect that it is upstream rather than downstream over-utilisation, and is probably made worse at the moment by WFH. Due to the technical architecture of the DOCSIS standards that apply to cable internet, there far less upstream capacity than downstream, and when lots of customers are on Teams calls or related uses that busts the assumptions that the network was designed with. For some punters, this is only the WFH pressures, and will resolve itself post-Covid. For some there's more than just WFH and the network has an underlying capacity problem, possibly not at the undemanding threshold at which VM do formally admit there's over-utilisation. And for that latter group it means that post-Covid the problem might still persist. We can't tell whether your problem will resolve as soon as/if ever the world returns to normal, but as many companies are adopting more flexible working models it's a leap of faith to assume that it will all clear up.
If you got the email/letter about the price rise, you've got 30 days (which is now ticking away) to tell VM you won't accept that, during which time you can ponder whether you do want to leave. If you do, telling VM you're cancelling normally starts a further 30 day notice period. If you time it right that's up to two months, which should be ample time to consider, decide, and if need be get a new ISP installed. Do it right, and you could have the new ISP in two-three weeks before the VM end date, and then if you find that the new ISP isn't delivering, phone VM and rescind your cancellation whilst cancelling your new ISP under cooling off rights. A bit complex to outline, but if you can follow me there's some good tactical options open to you.
